A laterally installing wheel having a rim in which a rim main portion and a side ring are detachably coupled to each other at a coupling portion thereof is proposed by the present applicant (Japanese Patent Publication 2001-239801). In the laterally installing wheel, a tire is laterally installed (i.e. in the axial direction of the wheel) on the rim when the side ring is detached from the rim main portion, and then the side ring is inserted onto the rim main portion and is fixed to the rim main portion by rotating the side ring about the axis of the side ring.
However, with the conventional laterally installing wheel, when viewed from outside in the axial direction of the wheel, the external appearance of the wheel needs improvement because a gap between the side ring and the rim main portion and a step at the coupling portion of the side ring with the rim main portion are visible.